CraigD, on 09 August 2010 - 11:48 AM, said:
I agree with maikeru’s suggestion,
except that I’m not sure if methane is a significant intermediate product when
generating electricity with microbial fuel cells. From what I gather from the linked article and its references, the most promising MFCs generate electricity from direct contact with a sugar and microorganism solution (typically processed sewage wastewater), with no need to generate methane which is then reform into pure hydrogen gas.
The methane comment mostly relates to the digester, in which many kinds of biomass feedstock can typically be fermented and used to produce methane for electrical or heating purposes. Microbial fuel cells are conceptually simple but require some tweaking and working with. But simple ones can be constructed for relatively cheap and using local ingredients, such as I imagine city or rural people might have access to. However, I wouldn't expect them to generate significant power yet without a lot more work and research going on. The reason I brought it up is that Ganoderma runs a farm and may have access to animal manure, which can also provide inoculants and be mixed with algae to be "anaerobically composted" in a MFC.
From Wiki:
Quote
Besides wastewater power plants, as mentioned before, energy can also be derived directly from crops. This allows the set-up of power stations based on algae platforms or other plants incorporating a large field of aquatic plants. According to Bert Hamelers, the fields are best set-up in synergy with existing renewable plants (eg offshore windturbines). This reduces costs as the microbial fuel cell plant can then make use of the same electricity lines as the wind turbines.
I need to research the details on MFCs again. It's been a year or so since I came across the ideas and researched them a bit. But I think they're promising for developing countries and rural areas, especially for farmers. Farmers have access to copious amounts of manure + crop biomass/feedstock.
Quote
When I hear mention of algae as an energy source, I don’t think first of it being used to generate electricity, but to produce high energy density combustible fuel that can be used in vehicles, especially aircraft. This is important, I think, because while Ganoderma’s assertion that
...
is IMHO true for the majority of applications, practical electric aircraft are still far beyond our near-term technological grasp, because the even the best batteries still weigh 40 to 100 times what an equivalent energy content of petroleum or algae-based jet fuel does (see the tables in the wikipedia article energy density). Aircraft being very weight and energy critical, such an extreme difference in energy density is a real show-stopper in replacing fuel-burning ones with electric ones. As non-renewable petroleum is replaced with renewables such as algae-produced oil, its scarcity and goodness for demanding applications like aircraft may make it too value to be used for applications that energy sources such as wind and photoelectric can satisfy.
Craig, yes and no, that's what I used to think too until I did a lot of research into what it takes to grow, produce, and refine biodiesel from algae. First, you need to identify and grow the right kinds of algae, and usually they have to be varieties that store and yield large amounts of processable fats or oils. I think they can be found in both fresh and salty water, and IIRC, they may be more predominant in colder waters. There are some varieties that can store 40-60% or maybe more of their energy reserves as lipids that we can extract and process into biodiesel. What most of the research is focused on is pure cultures of these varieties of algae, and it's the pure, monoculture crop production thing that is the problem. It's easy to maintain a pure culture in a lab, not so easy out on the farm, production site, or for that matter, any place exposed to potential contaminants found in the air or equipment which may contaminate the crop. This is why I said:
Quote
I wouldn't bother with conversion into biodiesel or something complex like that. If you did, you'd have to worry about contamination issues, growing the right kinds of algae, systems and efficiency, processing, refining, filtering, and purifying your oil, and headaches with complexity.
Nature abhors monocultures.
It is difficult and energy-intensive to maintain a monoculture crop of a certain species of high-oil-yielding algae. Doable on the small scale, but as ramps up to industrial-sized production, it becomes increasingly difficult to maintain purity and quality at an affordable price. And this is part of the reason why biodiesel from algae currently is cost prohibitive. From Wiki: "Dmitrov[52] examined the GreenFuels photobioreactor and estimated that algae oil would only be competitive at an oil price of $800 per barrel." (Here:
http://en.wikipedia....nomic_viability ) It may get cheaper, but I'd say it's not cost-effective unless algae biodiesel can be less than $150-200 per barrel, similar to or a bit more expensive than what we think conventional oil prices will rise to in the near future.
One further quote from Wiki illustrating my point:
Quote
Because algae strains with lower lipid content may grow as much as 30 times faster than those with high lipid content,[29] the difficulties in efficient biodiesel production from algae lie in finding an algal strain with a combination of high lipid content and fast growth rate, that isn't too difficult to harvest; and a cost-effective cultivation system (i.e., type of photobioreactor) that is best suited to that strain. There is also a need to provide concentrated CO2 to increase the rate of production.
Ok, considering all the above forget that. Let the experts handle that and the investors bear the brunt of expensive inquiry. There is one thing that algae is very good at doing, and it's multiplying like crazy and forming crazy amounts of biomass, so that's where I think the focus should be: biomass production. A focus on the highest, sustainable yields of biomass. And that doesn't require focusing on monocultures or genetic engineering or other complications a farmer, city dweller, or person in a developing country would care about. In fact, polycultures may yield much more harvestable or usable energy per acre/volume because they simply produce more biomass more efficiently. So focus on that. And focus on general, simpler, more efficient means of utilizing that high yield of biomass into the desired output (electricity). Algae biomass can be combusted, it can be fermented and digested, etc.
I agree with you on batteries, energy density and superiority of liquid fuels, etc. Just explaining why I think it's better to focus on biomass production, then deciding what to do with that biomass, than liquid fuels from the algae. Find what works well for your situation and go with it.
Edit:
PS. I want to mention that most production methods of oil from algae and research with high yields revolve around photobioreactors that rely on electrical lighting of some kind (LED, fluorescent or other) that use large amounts of electricity typically from non-renewable sources. So far, current strategy and implementation has been counterproductive to the goal of freeing ourselves from oil and moving towards a future of sustainable and renewable fuels, and is costly and another reason why biodiesel from algae is cost-prohibitive and resembles the "ethanol from corn" debacle we had a couple years ago.
http://en.wikipedia....gae_cultivation
Help
Join now
Sign in
Promote to Article
There are many different ways to start what i call cheap slurpy tanks. I would say if your a good farmer of algae and learn to mix properly for a good source of biogas, that would be the way to go wouldn't it?
